newbie questions about limit orders

If I place a limit order to buy above ask, lets say by accident, way above or slightly above ask, will it get filled at ask or have i just lost a ton of money, same thing for selling.
Also for short/cover orders, if there is availability it will be at ask or bid .
I plan on trading ETF SPY so liquidity is good and using direct access

SPY during trading hours normally has very liquid, tight markets. Your broker has a "best execution" requirement. That means they must give you the best price available at that time. You should never receive an execution outside the NBBO (National Best Bid Offer).

If I place a limit order to buy above ask, lets say by accident, way above or slightly above ask, will it get filled at ask or have i just lost a ton of money, same thing for selling.
Also for short/cover orders, if there is availability it will be at ask or bid .
I plan on trading ETF SPY so liquidity is good and using direct access

Thanks

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Before 2007 you would have lost a ton of money. Your broker would keep the difference between the best ask and your limit order. In 2007, RegNMS was introduced by SEC which obligates your broker to fill you at NBBO prices. So you are fine today. In Europe there are similar regulations with MiFID.

This is only for equity markets though. Does anyone know if similar regulations exist in Futures markets?

Before 2007 you would have lost a ton of money. Your broker would keep the difference between the best ask and your limit order. In 2007, RegNMS was introduced by SEC which obligates your broker to fill you at NBBO prices. So you are fine today. In Europe there are similar regulations with MiFID.

This is only for equity markets though. Does anyone know if similar regulations exist in Futures markets?

More...

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And if one askes a good question [it is a good question]about losing a ton of money on limit order ,,SPY, be prepared to do so, learning